为什么我的屏幕只有黑色？
out <- Reduce(function(...) merge(..., by = "row.names", all = TRUE), Bpam)
row.names(out) <- out$Row.names
out <- out[, -1]
因此，我试图创建一个方格图案，然后在屏幕上绘制它。 我已经在learningopengl.com上进行了练习……我不明白我在做什么错。 有帮助吗？
我正在使用C语言和OpenGL 4.5
我正在尝试学习现代OpenGL，我使用的是固定管道，在此之前，它在许多方面都大不相同。
答案 0 :(得分：6)
程序本身不会用数据填充元素索引缓冲区（ebo）。如果没有元素索引缓冲区，glDrawElements将无法从中提取元素索引，因此将无济于事。
编辑1：此外，顶点缓冲对象（vbo）仅用于着色器所需的3个属性之一。您只需要设置纹理坐标属性指针，而不能设置位置或颜色。
编辑2：另外，您没有将采样器设置为统一。
编辑3：最后但并非最不重要的一点是，您正在创建核心配置文件上下文，但是使用不推荐使用的格式（因此核心不可用）纹理格式GL_LUMINANCE。您必须为单个通道纹理使用GL_RED。
确实呈现棋盘格纹理的固定程序的源代码：
#include <epoxy/gl.h>
#include <GLFW/glfw3.h>
#include <stdio.h>
#include <stdlib.h>
//#include "include/state.h"
//#include "include/state_machine.h"
//#include "include/renderable.h"
const int WIDTH = 800;
const int HEIGHT = 600;
// called when user resizes window
void framebuffer_size_callback(GLFWwindow* window, int width, int height) {
glViewport(0, 0, width, height);
}
// called when we receive input
void processInput(GLFWwindow *window) {
if(glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, 1);
}
GLuint get_checker_texture() {
unsigned char texDat[64];
for (int i = 0; i < 64; ++i)
texDat[i] = ((i + (i / 8)) % 2) * 128 + 127;
//upload to GPU texture
GLuint tex;
glGenTextures(1, &tex);
glBindTexture(GL_TEXTURE_2D, tex);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, 8, 8, 0, GL_RED, GL_UNSIGNED_BYTE, texDat);
glGenerateMipmap(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, 0);
return tex;
}
//void render_box(renderable* this, unsigned int vbo, unsigned int vao, unsigned int ebo) {
// draw_texture(this->texture, this->x, this->y, this->z, vbo, vao, ebo);
//}
int main(int argc, char* argv[]) {
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // only on MACOS
#endif
// creating the window
GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "OpenGL App", NULL, NULL);
if (window == NULL) {
printf("Failed to create GLFW window");
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
// hook on window resize
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
glViewport(0, 0, WIDTH, HEIGHT);
// just making sure the state machine works
// for testing purposes only
/*state_machine* sm = init_state_machine();
state* state0 = init_state();
state* state1 = init_state();
state1->background_color->r = 1.0f;
state* state2 = init_state();
state2->background_color->g = 1.0f;
ss_vector_append(sm->states, state0);
ss_vector_append(sm->states, state1);
ss_vector_append(sm->states, state2);*/
//renderable* box = init_renderable(0.0f, 0.0f, 0.0f, &render_box);
unsigned int tex = get_checker_texture();
const char* vertex_shader_src =
"#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"layout (location = 1) in vec3 aColor;\n"
"layout (location = 2) in vec2 aTexCoord;\n"
"\n"
"out vec3 ourColor;\n"
"out vec2 TexCoord;\n"
"\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos, 1.0);\n"
" ourColor = aColor;\n"
" TexCoord = aTexCoord;\n"
"}";
unsigned int vertex_shader;
vertex_shader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertex_shader, 1, &vertex_shader_src, NULL);
glCompileShader(vertex_shader);
int success;
char infoLog[512];
glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &success);
if (!success) {
glGetShaderInfoLog(vertex_shader, 512, NULL, infoLog);
printf("%s\n", infoLog);
}
const char* fragment_shader_src =
"#version 330 core\n"
"out vec4 FragColor;\n"
"\n"
"in vec3 ourColor;\n"
"in vec2 TexCoord;\n"
"\n"
"uniform sampler2D ourTexture;\n"
"\n"
"void main()\n"
"{\n"
" FragColor = vec4(vec3(texture(ourTexture, TexCoord).r), 1.);\n"
"}";
unsigned int fragment_shader;
fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragment_shader, 1, &fragment_shader_src, NULL);
glCompileShader(fragment_shader);
int success0;
char infoLog0[512];
glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success0);
if (!success0) {
glGetShaderInfoLog(fragment_shader, 512, NULL, infoLog0);
printf("%s\n", infoLog0);
}
unsigned int shaderProgram;
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertex_shader);
glAttachShader(shaderProgram, fragment_shader);
glLinkProgram(shaderProgram);
unsigned uniform_sampler_ourTexture = glGetUniformLocation(shaderProgram, "ourTexture");
int success1;
char infoLog1[512];
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success1);
if(!success1) {
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog1);
printf("%s\n", infoLog1);
}
float vertices[] = {
// positions // colors // texture coords
0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, // top right
0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, // bottom right
-0.5f, -0.5f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, // bottom left
-0.5f, 0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f // top left
};
unsigned elements[] = {
0, 1, 2, 2, 3, 0
};
unsigned int vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
unsigned int vbo;
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(0 * sizeof(float)));
glEnableVertexAttribArray(0);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
glEnableVertexAttribArray(2);
unsigned int ebo;
glGenBuffers(1, &ebo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);
// render loop
while(!glfwWindowShouldClose(window)) {
processInput(window);
//state* current_state = ((state*)sm->states->items[sm->stateindex]);
glClear(GL_COLOR_BUFFER_BIT);
// render here
glClearColor(
0.2f,//current_state->background_color->r,
0.3f,//current_state->background_color->g,
0.3f,//current_state->background_color->b,
1.0f//current_state->background_color->a
);
glUseProgram(shaderProgram);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, tex);
glUniform1i(uniform_sampler_ourTexture, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 0;
}